Polyvinyl halide latices stabilized with diammonium phosphate and ammonium hydroxide



United States Patent POLYVINYL HALIDE LATICES STABILIZED WITH- I DIAMMONIUM PHOSPHATE AND AMMONIUM HYDROXIDE Isadore Nathan Cooperman and Milton W. Kline, Leominster, Mass., assignors to The Borden Company, New York, N.Y.

No Drawing. Filed Sept. 17, 1965, Ser. No. 488,233 3 Claims. (Cl. 260--29.6)

ABSTRACT OF THE DISCLOSURE This invention relates to vinyl halide polymers and copolymers thereof in aqueous emulsion. More particularly it relates to aqueous emulsions of said polymers and copolymers which are stabilized in the presence of iron ions while alkaline pH levels are maintained in the latex.

Vinyl halide polymers and copolymers thereof may be prepared in aqueous acid or alkaline pH media. Alkaline polymerization has been used to advantage in cases where the catalyst of polymerization is sensitive to low pH conditions and is subject to degradation by the acid as for example potassium persulfate. Another advantage of alkaline polymerization is the chemical stability of the latex when combined with additives in the same alkaline pH range. A significant difference between the pH of the latex and the additive causes the latex to coagulate (become unstable). It has been found that even though polymerization has been initially carried out in the alkaline pH range, the pH of the latex drifted lower during storage over a period of several months thereby causing instability when subsequently combined with the additives. Addition of alkali and other bases to the latex does not prevent the drift of the pH. It is believed that the downward pH drift is enhanced by the presence in the latex of free iron ion. Although invention is not based upon this proposition, it is thought that halides of iron are formed by breakdown of the polymer which on hydrolysis forms the halide acid. Usual chelating agents added to the latex are ineffective to prevent downward pH drift.

The present invention provides an economical and unique method for substantially preventing inter-action between iron ion and halide polymer while concurrently preventing the downward pH drift of the latex while in the alkaline range.

Briefly stated the invention comprises a vinyl halide polymer and copolymers thereof in aqueous emulsion and a stabilizing agent for the polymer in the emulsion. The invention also comprises the method for stabilizing the latex in the presence of iron ion while concurrently maintaining the pH of the latex in the alkaline range. The stabilizing agent comprises diammonium phosphate and ammonium hydroxide.

It has been found that diammonium phosphate and ammonium hydroxide act to reinforce each other, in other words, there is a synergistic effect when the combination of these compounds are included in an alkaline latex. The downward pH drift over a period of time is 3,403,123 Patented Sept. 24, 1968 substantially abated indicating that iron ion is tied up. The latter conclusion is supported by data showing latex stability in presence of iron.

As to materials the vinyl halide polymer may be any of the polymers or inter-polymers of which vinyl halide monomer is present in major proportions, as greater than 50% by weight. Vinyl halide monomers include vinyl chloride, vinyl bromide, vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride, vinylidene fluoride and the like. Other monomers copolymerizable with said vinyl halide monomers include acrylic and methacrylic acid, alpha-hydrogen substitution products of acrylic acid such as halogen and lower alkyl, C -C esters of said acrylic and methacrylic acids, C -C alpha unsaturated dibasic carboxylic acids and anhydrides and C -C esters and partial esters of said dibasic carboxylic acids as for example maleic, fumaric and itaconic acid. Other copolymerizable monomers include vinyl esters of C C acids as for example vinyl acetate, vinyl stearate and other similar polymerizable materials.

Other materials in the latex may include standard materials generally used in the polymerization and copolymerization of vinyl halide monomers. These include water soluble peroxy catalysts such as sodium persulfate, potassium persulfate, ammonium persulfate, sodium perborate, potassium perborate, and hydrogen peroxide. The preferable catalyst is potassium persulfate.

Surface active agents may be included, such as sodium oleate, sodium stearate, ammonium oleate, potassium palmitate, sodium myristate, and rosin or dehydrogenated rosin soaps. There may also be used synthetic saponaceous materials such as alkali fatty acid sulfates and alkaryl sulfonates, as for example, sodium lauryl sulfate and sodium isopropyl naphthalene sulfonate. Other agents include such materials as the dialkyl succinamates, the sodium salt of N-octadecyl-N-1,2-dicarboxyethyl sulfosuccinamate, and the like. Mixtures of two or more agents may also be used.

Other materials include modifiers for the polymer such as mercaptans, chloroethylenes, aldehydes, and synthetic and natural colloids such as polyvinyl alcohol, casein, lecithin, methyl cellulose, etc.

As to proportions, the monomer comprises vinyl halide in major proportions, in other words at least 50%, and preferably 70% and up to by weight of the total monomers in the system.

The proportion of additives to the latex are within the usual range such as between about .010.5 part of catalyst for 100 parts of monomer, 0-10 parts of surface active agent for 100 parts of monomer, 0l0 parts colloids for 100 parts of monomer, and 0-10 parts of modifying agent for 100 parts of monomer.

As to the stabilizing agent, diammonium phosphate compound is used in proportion of between about 0.1-1

part by weight for 100 parts of monomer. The preferred Example I Vinyl halide interpolymers may be prepared by reacting the monomers in the presence of additives in an agitated vessel at elevated temperatures, as between 75 F. Polymerization time varies with conditions, reactants and additives employed. It has been found that 3 4 the following typical formulations require about 16 hours At the end of regular time intervals the strips were reat a temperature of about 125 F. in aqueous medium. moved, rinsed, dried and weighed. The weight increase (Proportions are parts by weight.) was taken as coagulum buildup.

TABLE III.GRAMS OF COAGULUM (DRY) ON METAL STRIP Latex- Latex- Latex-(NH4)2 Latex-(NHQ HPO HPO Latex- KHQPOJ KHzPOl 4 4- Latex-(NHm Time (hours) KH2PO4 1 drop drops NHrOH- N HiOH- HPO4-NH4OH "Fe-3 Fe-3" 1 drop 20 drops 1 Only column (6) is part of the instant invention.

TABLE I The data shows the stabilizing agent is as good as the A B generally accepted standard for coagulation stabilization du 0 iron in latices. 'inyl halide r(nok1l1oln1er (vinyl chloride) 100 80 e t omonomer at y acry ate 2O Surfiace atitive agent (sodium dodecylbenzen 3 Examp 1e IV su lonate Catalyst (potassium persulmte, latex q Example IA 18 p d except h the Stabjiglizing agent: h 1 t 5 5 vinylchloride is replaced separately and in turn wlth the 1.3711131011111111 p osp l3. 0 c Ammonium hydroxide u 1 1 other vinyl halide monomers herein disclosed.

Example V The latex of Example IB is prepared except that the ethyl acrylate is replaced separately and in turn with the other monomers copolymerizable with said vinyl chloride monomer herein disclosed.

Example II.(pH stabilization) By way of example latices were prepared as in Example I except that other bases and phosphate compounds as well as the separate components of the stabilizing agent of this invention were substituted for combined diammonium phosphate and ammonium hydroxide. The Ex l VI pH decay was noted and compared with a latex prepared as in Example IA. The proportions of the base and phosphate compound are as shown in Example I.

The latex of Example IB is prepared except that the vinyl chloride is replaced separately and in turn with the other vinyl halide monomers herein disclosed.

PE H The pH decay characteristics and coagulation stabilip zation properties of the latices of Examples IV-IV are (1) (2) (3) (4) comparable to Column 4 of Table II and Column 6 of Time Nrnorr NMHPO4 (NHmHPor (NHnrHPor Table III. (days) NaOII NH-lOH The latex is useful in the area of coatings namely, to

9.0 0.0 7.5 9.0 protect and add color to substrates such as textiles, plas- 2'3 2 2 Z12 Z 3 ties as for example vinyl sheeting, and also to various 8.0 8.3 7.3 8.9 cellulosic materials such as Wood and paper. Usually, the $18 3% Q3 2:: latex is applied as by spraying or other coating methods 7.1 7.5 6.2 8.0

to the substrate and the carrier is evaporated from the surface leaving a continuous film of polymer coating.

It will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitute departure from the spirit and scope of the invention.

What is claimed is:

Example III.(Coagulation stabilization) 1. A method for stabilizing an aqueous latex in the presence of iron ion and preventing substantial pH decay, said latex including a vinyl halide selected from the group of vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene chlorofluoride, and vinylidene fluoride, comprising the steps of:

(l) admixing therewith a stabilizing agent consisting essentially of diammonium phosphate in the range of 0.11 part by weight for 100 parts monomers used in said latex, and ammonium hydroxide in an Only Column 4 is part of the instant invention. The data shows that the stabilizing agent of this invention provides substantial reduction of the pH decay over a period of at least 40 days, and especially over the first 10 days. Other tests show that there is a comparable difierence in pH drop over a period about 3 months.

Latices were prepared as in Example I except that potassium phosphate was used in place of diammonium phosphate and ammonium hydroxide. KH PO is used to illustrate results obtained when previously known additives are incorporated into the vinyl latex in connection with an iron complexing agent. Varying proportions of Versene Fe-3 Specific were added to the latex as well as to other latices made with (a) diammonium phosphate, with (b) ammonium hydroxide, and with (c) L diamrnonium phosphate plus ammonium hydroxide. These amount Sufliclent to false the PH of the systam mto were compared to a latex with diammonium phosphate the range f 9 and and ammonium hydroxide, but with no Versene Fe-3 (2) Polymenzmg sald y hallde the Presfince Specific dd d said stabilizing agent.

Versene Fe-3 Specific is a trade name for an organic The met h0d 0f t 1 w ein: complexing agent that forms extremely stable complexes 531d Vinyl hallde 1S p y 'l f Wlth monowith ferric iron in the pH range of 3.5 to 12.5. The mm Selected r the group cqnslstgng formula of the active ingredient is given as an acryhc and methacrylic acid,

(b) halogen and lower alkyl alpha-hydrogen sub- CBHIZONNa stitution products of acrylic acid, gms. of the various latices described were placed (0) C -C esters of acrylic and methacrylic acid, in 8 oz. glass jars. A 1" wide, pre-weighted strip of sheet ((1) C C alpha unsaturated dibasic carboxylic iron metal was placed into each jar and the jar closed. acids and anhydrides,

5 6 (e) C -C esters and partial esters of said dibasic (b) ammonium hydroxide in proportion sufiicarboxylic acids, and cient to raise the pH of the system into the (f) vinyl esters of C -C acids, and range of about 7.5-9.5 (2) the weight proportion of said vinyl halide is at (c) and polymerizing said vinyl chloride monoleast 50% of the total weight of said copolymer. 5 mer in the presence of (a) and (b). 3. A method for preparing an aqeuous polyvinyl ehlo- I ride latex which is stable in the presence of iron ion and References Clted which exhibi:s su'bstanial pH stability against decay UN D STATES PA S com-prlsing t e steps 0 v (1) admixing with a vinyl chloride monomer, a sta- 1O 2233 et bilizer consisting essentially of (a) a diammonium phosphate in proportion of R about .3 part by weight for 100 parts of poly- MU RAY TILLMA N Prlmary Exammer' 'vinyl chloride, nd W. J. BRIGGS, Assistant Examiner. 

